1. Field of the Invention (Technical Field)
The present invention relates to thin film hydrous metal oxide catalysts; and methods of making and using such catalysts.
2. Background Art
Hydrous metal oxide (HMO)-supported catalysts, such as palladium, platinum, rhodium, or nickel-molybdenum type catalysts on alkoxide derived hydrous titanium, niobium, zirconium, and tantalum oxides are generally superior to the several available commercial catalysts. One of their drawbacks, however, is higher cost due to raw material expense. Further, such HMO-supported catalysts have to be manufactured in a suitable engineering form, for example, grains, spheres, extrudate and the like, which entail even higher cost.
U.S. Pat. No. 4,511,455 to Dosch et al., entitled Catalysis Using Hydrous Metal Oxide Ion Exchanges, describes a method for preparing bulk hydrous metal oxide catalysts using ion exchange to load various active metals. While various shapes of catalyst are suggested, there is no disclosure therein relating to thin film catalyst formation upon inert supports.
However, by preparing hydrous metal oxide thin films (&lt;100nm) on inexpensive inert supports, the favorable catalyst properties of the HMO materials are retained or even enhanced, but the expensive components of the HMO materials are only 10% or less of that comprising bulk hydrous metal oxide catalysts. Further, the physical properties of thin film HMO catalysts such as surface area and pore size distribution, can be determined by commercially available engineered materials, rather than the properties of the bulk HMO material. This, of course, eliminates the need for research to convert HMO catalysts to usable geometric forms and provides more choices with respect to physical properties. The present invention is partially described in Development of Thin Film Hydrous Metal Oxide Supported Catalysts for Direct Coal Liquefaction, Dosch et al., Proceedings Liquefaction Contractors' Review Meeting, Pittsburgh, Pa. (published 1992), the teachings of which are incorporated herein by reference.
Additionally, virtually any surface, porous or non-porous, which permits atomic dispersion of the active metals, can be used. For example, metallic structures or quartz sand as well as porous materials such as silica gel or alumina, comprise suitable thin film HMO catalyst supports.